San Diego, CA --
In the past, a PV system with battery storage was associated with the off-grid system — not connected to the utility grid. The battery stores the energy produced by the PV system and when the sun goes down, electricity is drawn from the battery. In Japan, the battery became attractive to store electricity from "the grid," to reduce electricity bills.

After the devastation of the Tsunami and nuclear meltdown in Mach 2011, Japan became painfully aware of the importance of both safety and maintaining a steady supply of electricity. The combination of a PV system and battery storage gives consumers the ability to produce, store and supply electricity throughout the day at their own home for power outages and emergencies. However, the system can bring economic benefits — electricity bill reduction — during normal days.

Like California, utilities in Japan offer Time-of Use (TOU) rates. How homeowners can reduce electricity bills can be illustrated by using Tokyo Electric Power Company’s (TEPCO) current (non-summer) TOU rates for all-electric homes with a PV system.

Sell PV-generated electricity to the utility at the FIT premium rate of ¥38.0/kWh [US $0.38]

Use PV-generated electricity during day time, otherwise paying at ¥30.77 (10 am – 5 pm) [US $0.31] and use stored electricity between 7 and 10 am and between 5 and 11 pm, otherwise paying ¥25.2/kWh [US $0.25]

With the battery storage, PV homeowners can ultimately buy electricity at the lowest rate (¥11.82/kWh or $0.12/kWh) and sell at the highest price (¥38/kWh or $0.38/kWh).

The key domestic PV makers, Panasonic, Kyocera and Sharp, all now offer lithium-ion battery storage along with a PV home system to meet consumers’ demand. Their goal is to move beyond PV and expand into a total Home Energy Management System (HEMS3) arena.

In April, Kyocera released the largest residential lithium-ion battery in Japan. The battery has the capacity of 14.4 kWh, which is priced at an MSRP of ¥4.45million [US $43,784]. This large capacity allows it to power a home refrigerator, TV, computers, lights and cell phone chargers for up to 24 hours.

Kyocera has teamed up with Rakuten, Inc., which operates the nation’s largest internet shopping site, to offer a PV system (poly-Si) and a lithium battery (7.2 kWh) set for homeowners at an affordable price. Rakuten provides options with different sizes of PV systems with the battery, and installed system price (after tax) varies from ¥2.94 million ($29,730) with a-2.28 kW system to ¥4.168 million ($42,153) with a 6.27-kW system. These systems are installed by one of the nation’s largest installers, Nippon Ecosystem, which is part of Itochu Corp.

Residential battery systems remain expensive to average homeowners. To solve this issue, One Energy Corp. has just begun the nation’s first residential energy storage leasing service. Like SolarCity or SunRun’s PV leasing service in the U.S., this requires zero upfront payment to homeowners. The company is a joint venture between Orix, NEC and Epco. NEC provides lithium batteries, whose technology is used for Nissan Leaf electric vehicles.

Besides the energy storage leasing service, One Energy also offers “Yanekari (PV rooftop space leasing)” service. A homeowner can lease a storage system with 5.53 kWh of capacity at between ¥3,045 ($31) to ¥5,145 ($52) a month from One Energy while offering the roof-space to One Energy, making a monthly revenue of ¥2,500 ($25). The image below illustrates how a customer could use an energy storage system to offset the high cost of purchasing energy during peak times.

One Energy currently offers this leasing service in the TEPCO region only and is planning to expand to the Kansai region by the second half of this fiscal year and eventually expand nationwide.

NEC started mass production of residential storage systems in February. Besides partnering with One Energy, the company sells home batteries directly to homebuilders and building material distributors with the goal of selling 15,000 units during this fiscal year.

The company stated that PV homeowners will start storing PV electricity in batteries even more as the FIT rate gets lower in the future, creating a more self-sufficient and less grid-dependent environment.

It is declining, but the national government provides upfront, capacity-based rebates (¥15-20/kW) and a net FIT of ¥38/kWh on excess electricity generation for 10 years) for PV home systems. The government also currently provides a subsidy for lithium-ion battery storage for homeowners. The subsidy is one third of the installed system cost or up to ¥1 million ($10,823).

The hot and humid summer is approaching in Japan. Some of the nation’s utilities have just raised electricity rates and many of them will request that consumers limit and/or shift electricity consumption from peak to off-peak to control raising fossil fuel cost caused by the shutdown of nuclear power plants. With PV + battery systems, homeowners are moving to take energy matters into their own hands in defense against rolling blackouts and rising electricity bills.

27 Comments

Just registered. I live about 80 km from Fukushima. I have PV solar and I am knowledgeable. I was here for the quake. It was a doozie.
I think everyone here can follow the math, but if you look at the pricing and the FIT, it might not be clear how one does or does not benefit from the battery.
I want to explain that, but first let me say that estimates of recovery from the quake posted above at comment 18 are "out there". Bottled water for weeks/months? Maybe on the coast, but in this immediate region it was about a week. Roads and highways were up in short order, with buses and trains. Gas took about two weeks. Gasoline took longer. Nuclear hysteria caused more problems than anything. Anyway, your mileage may vary, but Japan did a great job. Many preppers. No doomsday preppers.

During that time, I had power when the sun shone. If I had a battery or PEV plug in vehicle, I suppose I could have extended that, but the grid where I lived was up in three days. It was a weekend, so it went out on Friday afternoon and was up on Monday morning.

For reference, many plug in vehicles have about 12 kWh in them, so if you had one, you would probably not need PV storage with a dedicated battery.
The load management of these PV storage batteries is attractive, but I am not enthusiastic. Assume a FIT of 42 yen. Assume 1000 kWh used per month. Assume half of that is peak, at about 33 yen, and half is off-peak, at about 9 yen. You want to sell all you can during the day at 42 yen, naturally. And you want to cut your line power consumption to zero if possible. 4.5 kWh in a battery will not do both.
If you can only do the latter, for whatever reason, you are saving the difference of 33 and 9 yen, or 24 yen per kWh, and on 500 kWh per month. Let's call that 100 bucks a month. You will break even in about 10 years.
One third is subsidized. Low interest rates. Maybe you can protect some FIT revenues. 100% efficient Li batteries won't last that long. It is a wash at best.

mark-smolinski, I had kept a backup generator in my house for years. In the end I replaced it with a permanently installed NG/propane generator that is on an automatic transfer switch.

Lead acid batteries are a pain to deal with, they have maintenance cost as well as disposal costs. Lithium Ion has the higher energy density needed for the system described by Junko to work - and perhaps even be cost effective in some regions of the US.

The designers formed an alliance that meets multiple needs an it provide TOU peak shaving. That shaving ability is what reduces its cost and makes it practical in Japan. Germans are rolling out similar systems. In most locations of the US it would not pay -- our rates are just too low and we have other good alternatives.

Standby generators are also sometimes tightly controlled in urban areas because of the "noise" pollution and exhaust emissions. The system described in the article would work for those cases.

Certainly the system Ron suggested would work in may US locations, perhaps excluding the sink hole prone areas of Florida...

The authors story was about a system that is now being sold, easily installed, supported locally, available from a large retailer, that provides long term emergency power, renewable energy for their daily use, peak shaving, it is produce in Japan, it provides the 100Vac based power that their homes and appliances expect, it provides 50hz electricity for eastern Japan and 60hz electricity that the western Japan grid uses.

They have a solution. The system described by Junko could also be adapted for sale within North America. I suspect the US markets will see it offered (lithium ion based) within two or three years by similar alliances with the existing US inverter suppliers.

Re: Lead acid., #22
In FL, lead acid batteries have a life of 3-6 years. PERIOD. I have played this game with all sorts- deep cycle, house, etc. (in a boat) With the periodicity of hurricanes (not that frequent), I simply can't see wasting money on something that has that little longevity, along with memory, equilizing charges and all the rest. Simply not interested. Also not interested in Lithium at current pricing. It is better, for all intents and purposes, to let generator sit in garage and fire it up occasionally- and use if ever needed. Just as with my Chevy Volt's generator, my gasoline generator is my bridge until renewable energies are available at reasonable prices. I love my solar pv, but it functions 365 days a year. It is renewable worth having and using. But renewable that may never be used (for backup) is just not worth it for now.
Also, lithium may also prove pointless if other battery technologies get perfected where weight is no issue, but cost is reduced. Energy density may be valuable in automotive applications, but home backup is entirely different. I am sitting on the sidelines for now.

I might have a solution the KW3 cube. It is a complete outdoor stand-alone solar generator with hight power batteries of 6000 cycles so 4 times classical 1200 cycles. It is watertight and dustight, silent running, maintenance free.it has its own safety control system to provide electricity day and night and it plays also a back-up system to filter harmonics in case of outrage. They have thought to provide a 5 years warranty on the cube and 20 years on the batteries. it could be the product needed by Japan.

Hi #11: As backup power a 5 year lead acid can do 7 to 10 years if maintained correctly. As backup, its life is really just sitting with occasional over charge to balance and shake up the acid. Perhaps the price difference did not fully sink in. $11,000 for 5 KWH is $2200 per KWH!! $3600 for 32 KWH is about $110 per KWH!! That's a TWENTY FOLD DIFFERENCE!! Even at a life of only 5 years on the lead acid, for equal money that's 100 years before I would pay the Li cost... I do everything on a shoe string $$ wise, no choice.
If you have the money available and have physical limitations, fine.. but other wise I can think of better things to do with a twenty fold difference....

Ron, I understand you like using the system you have referenced, but remember those cracks in the foundation... they've also damaged the bore holes. All that liquid-faction of the soil has rendered them useless... the boreholes collapsed.

The system Junko is describing can tolerate and ride through the earthquake. It is a reasonable clean, efficient, system with few moving parts. It would be easy to adapt over time if needed.

300kM east of where I live, the exergy/storage system would work well -- and the earthquakes wouldn't be a problem. But that area of Washington has hydro power going at about $0.04/kWhr. That becomes hard to beat -- and it is already renewable.

exergy/storage systems need to be matched with the application to be succesful -- just as solar, wind, geothermal, biomass, etc systems need to be placed in the correct market. A biomass system designed to use cow manure and produce electricity from methane is a great idea and they work well -- when placed next to a dairy farm. Put that same system at the south pole and it is a total waste - good system still, but not a good application of the technology.

Well, since the last couple of comments have gone the way of deprivation, I'll add a couple things. When my house was built in 1996, I had 7500 gallons of buried cisterns installed- even though I live in an incorporated city of approximately 17,000. I did this because water wars were already being fought, and the long term availability of inexpensive, pure water was in doubt. Since I got rid of ALL my grass a few years ago (replaced with lots of drought resistant plants, artificial turf, walkways, concrete circular driveway), I haven't used a drop of city water. Now, we are being told that our drinking water is filled with excreted pharmaceuticals, frack waste, and all other nasties. I am not only set for extended states of deprivation on the water source front, I get the cleanest stuff you can get (metal roof too). And then I installed solar hot water heating, with a solar pv driven circulating pump- so those showers are never cold either. Like I mentioned previously, the only thing I await is practical power storage and I am up for an episode of 'Doomsday Preppers'.

Dennis: You are on your own for water and sewers but in the future a home's energy requirements could all be met by storage systems for any length of time via a combination of exergy/heat storage (in a locale that has substantial seasonal temperature variations) and short term electricity storage, preferably using future PV panels that achieve the kind of performance that is being demonstrated in some of the current lab examples. You can combine PV and solar thermal in the same box to make a collector that utilizes nearly all of the incident radiant energy and the concentric store can store it at a high enough temperature to retain sufficient exergy.

Ron, If the power is out for somewhere between two and six months how well does the system work. That is the basic issue for the Japanese system being proposed. It is actually very relevant for my house in the Seattle area. Like Japan, we have some major fault lines and average a 9.0+ earthquake about every 400 years. The last one off the coast was 1700. So looking for resilience becomes critical.

In a major earthquake, > 7.0, you almost always loose electricity for a while, you often loose, water, possibly sewer and gas. When the earthquakes hit 9.0, the conditions are:

1) roads / bridges are closed for weeks. Bridges gone for perhaps a year
2) transmission lines are down, bulk generation is gone, hydro dams, perhaps compromised, nuclear offline, shipping ports damaged, airports damaged - weeks/months before repairs are complete.
3) water lines shattered, for weeks/months - it is bottled water
4) sewers are compromised by shifting ground, diesel generators to used to fuel them, fuel is reservered for critical needs like hospitals, sewers, some water filtration, etc.
5) natural gas is not available - work to repair is months out.

Sounds nasty right, this is actually the scenario that is expected in Seattle and the surrounding area. It is based on past historical records from the area, it has been adapted from the experiences in New Zealand and Japan.

So with this in mind look at the system the author talks about, power is lost, the house might still be standing, cracks in the foundation, some structural damage, windows cracked but now with plastic on them. No water, sewer is iffy, no gas. But they do have limited power from the solar above and storage batteries. Enough to boil water, charge cellphones, and some lights. BUT NOT enough for heat pumps. Full electric service is still months away (think Hurricane Sandy as another example).

Dennis: All storage batteries are load shifting devices - they are inherently different from flashlight batteries, for example. Exergy storage provides peak shaving, load shifting and most of the energy needed for heating, cooling and DHW in the case of a power failure. In theory it could also provide the relatively small amount of power needed for control purposes in the event of a power failure but in practice it is more practical to provide a little bit of stand-by power for that purpose.

We will all have to learn to do things differently in a fossil fuel-free world. At one time every house had its own well and its own septic tank, but now we share such plumbing. I think that in future we will also share energy storage facilities, for example with one energy store on each city block (as described in my article). That will happen in Tokyo, Tucson and Tuktoyaktuk, but of course people will fight it to the bitter end. The heat/exergy stores can easily be placed under city streets so providing space for them is not a major issue.

Ron, the system you reference is for load shifting only. You would still need battery storage to run the pumps with an extended power outage to extract the stored power. The author's story is about the use of solarPV with lithium ion batteries that provides peak shaving, load shifting AND in the case of a disaster standby power.

Winters in the Tokyo area are similar temps to Seattle, cool, snow is uncommon, the summer time can get quite hot and muggy (at least by my standards) But it means that they might only need 10K-20KBtu/hr for heat pretty low requirements. Mini split heatpumps are commonly used in Japan and they are LOW COST (much lower cost than we see in North America). Domestic Hot Water requirements are also lower.

The Panasonic Power Panel is a big difference from a straight solarPV inverter that is often used. It is also much more different than the grid-tied/lead acid standby combination that are commonly installed in the North America and Europe. This is would be more like an V2G combination from a car - with the large 4kW solar panel on top.

The system storage system you describe is good, but it is for an entirely different market. I have seen (and touched) similar systems. A large business office sized system 16kM from my location is the new Bullitt Center building. www.bullittcenter.org

Ground storage works well with the right soil conditions and if you have enough room to sink the wells. Many of the areas that are served by TEPCO have a very high population density. Imagine the battles you might have if individual homes/businesses would try sinking the boreholes in the narrow historic sections of old Quebec city. Many of the older TEPCO served residential areas are very compact.

Near my house they work fine, but my parents house in MT, it doesn't work -- water underground is cold AND moving.

@Mark - yeah, I know that. My point was that GM should develop V2G capabilities so that one can use the batteries in a Volt (or any other car with a decent amount of battery capacity, even hybrids like the regular Prius can function this way) to help provide emergency backup power.

Without being able to easily tap the HV battery, most people run a 1 kW 12VDC-AC inverter for small loads, which still doesn't leave you with a good way to charge your car with your solar system unless it's an off-grid system already with batteries.

@drees
Current Volts are not meant to tap into the batteries (for real). Some have developed kits which get right to DC bus connections, but GM threatens voiding warranty. The loads that people have tapped for are relatively light. I am looking for more robust backup. I have mentioned to others that the next time I will upgrade my vehicle(s) is when the car can interact with the grid, V2G. My (portable) gas generator back up will be sold off at that point. I bought it after Charley in 2004, but it has yet to be used for real (I run it periodically just for maintenance). But it is frustrating indeed knowing that I have MUCH more capable generators in those Volts that will not help my back up situation (at present). I think the concept is awesome, and was just telling someone about the Via Motors offerings coming soon. Having Lithium Ion onboard means that the generator can cycle, unlike regular generators which run constantly. So much promise in what lies ahead.

junko-movellan: The article in Sustainability-Journal.ca did in fact use a home as the example, although the design can be applied to any type of building. It is not a ground-source system that would be eligible for the FIT rates you referred to.

The storage capacity of an exergy storage system is 5,000 to 10,000 kWh per home (not including the thermal storage that is used to heat the house), which is considerably greater than the 5 to 17 kWh capacity of the batteries in your article.

I live in Canada, where we have relatively cold winters and hot summers, so both the storage need and the available capacity are higher here than in Japan. It costs several thousand dollars per home to add the electricity storage to the thermal storage that is used for space heating but for that you get a huge increase in capacity and the ability to store both heat and power for long periods of time.

@Mark - Well, obviously if you already have 32 kWh (about 20 kWh usable) sitting in two Chevy Volts, ideally you'd simply tap your Volts for the odd power outage. With a full tank of gas you could power your house for a long time (especially only running critical loads) and indefinitely if you could charge the Volt with rooftop solar.

A handful of extra cycles a year isn't going to affect their life any significant amount and the batteries are fully capable of handling any reasonable household load.

What is needed is a decently priced house-to-home inverter. I know that Nissan has produced one for the LEAF / Japanese market which taps into the car using the CHAdeMO connector. Unfortunately, J1772 does not provide for any car-to-grid power capabilities...

As a PV owner who has had the eye of TWO Cat 4 storms strike his house (Hugo, Charley) and lost power for weeks at a time (with both of them), I think of this power back up thing often. I will NOT go lead-acid, EVER. They just have too limited of a life on them. And as the owner of TWO Chevy Volts, I know that if properly temperature regulated and not fully charged/discharged, Lithium batteries can last well beyond a decade. It is that kind of longevity I am waiting for- but the price has to come down. I was looking in this discussion somewhere to see if temperature control and charge regulation is accommodated on these residential systems. I am happy that there is a demand for this product; it will make my wait shorter by helping to establish a market and drive down the price. Also, my FPL power is too cheap to have enough price swing between regular and TOU plans to help pay for this system. I am only interested in Lithium batteries for power outages. And (absent a hurricane) our power here is pretty reliable. The biggest source of power outages is tree limbs (usually from wind) which fall on power lines. Southern Florida has few trees to cause this effect.

Thank you, Dennis.
Yes, this story is solely on the residential segment, excluding non-residential and utility segment.

The federal government also currently supports this emergency preparation by providing a subsidy of 1/3 of the battery installed cost.

Japan also tries to diversify renewable energy mix besides PV. The FIT rate for geothermal system below 15 MW is 42 yen/kWh (~$0.42/kWh) for 15 years and system over 15 MW is 27.3 yen/kWh (~$0.27/kWh) for 15 years.

Ron, I read a lot of articles, and I've seen similar. The Japanese are looking for small distributed storage that can work in dense populated areas, That was the intent of the authors story. They have lots of other medium and larger scale storage available and they use them.

You also need to remember the environment that they are in. The country is part of the ring of fire, they have many earthquakes, drilling wells for energy storage - when the ground is shifting over years can be a problem. Pumping stuff into the ground can cause concerns with neighbors, pulling geothermal heat out of ground causes concerns with neighbors, and in most of the little towns, you don't have the wide streets you need to setup all the well drilling equipment. The application of the technology needs to match the cultural and physical needs of the customers.

Again the story is addressing single family homes/appartment with roof top solar - for their immediate energy needs.

Dennis: If you read the article I referred to you will see that such systems extract a very large amount of energy from the air. They also make intermittent sources like solar and wind energy more practical by handling both periods of excess energy and deficit periods. Although they use the ground for storage they do not normally either extract or contribute any net heat to the ground on an annual basis. As you note Japan has a considerable potential for using deep geothermal heat, but even stable energy sources need storage to cope with load variations.

hoppe-w, The authors story is about Japan, their energy energy consumption in the typical residence is quite low. The climate is moderate, cooling perhaps and for dehumidification. In the eastern part of Japan they have an energy crunch because of shutdown nuclear plants. Adding solar to residences helps that out as well as storage to smooth the peaks.

RonTolmie, before you can store it, you need it. They are adding storage as part of a residential solarPV program. This is a big push out to help the grid after the 2011 earthquakes and to make their grid more resilient in the event of future disasters. Japan is on the ring of fire and they have geothermal resources they can build out. Those resources take longer because of siting concerns; and real concerns that the geothermal wells might damage the naturally occuring hot water that is used for traditional Japanese baths.

When the article says, "The battery has a capacity of 4.65 kWh and is priced at ¥1.218 million MSRP [US $11,984]," does that mean the battery can safely frequently deliver 4.65 kWh without damaging the battery? Is this when the battery is new or is it an average over a reasonable period of time, like 10 years?

@william 'why would anyone go Li when weight is not an issue' That depends on where you live: I worked with a 30 something bachelor colleague who could get no other accomodation than his parent's 1 bedroom apartment unless he got married. Not much living in Japan is about a monster home on a cul-de-sac with a pool in the back. I keep my LA in a utility shack and given the management issues of the most efficient LA batteries and the insurance costs, that's by far the best place - not parked under the coffee table.

The good news is that Japan can create a healthy market for the very user-friendly technology which, like with the Prius, when they get the wrinkles out, they can make a lot of money selling it to people in California.

Electricity can be stored in ground in the form of exergy (thermal energy) at a tiny fraction of the cost of using batteries. The storage can be controlled by the power grid operator who can switch the storage ON at will and can subsequently recover the same amount of electric energy with the Recovery switch, so it functions like a battery. The details are described in the May issue of http://Sustainability-Journal.ca .

The best and most effective storage is control of consumption! This requires smart grid electrical power consumption counters, which are provided by a real-time price per KWH. You could even make negative prices in time periods with too much renewable energy generation. If this would be available private users would control their washing-machines and dryers, disc washers etc. to operate, when price is low. Even the installation of e. g. some KWH lead acid batteries would be thought about to take benefit from the price advantage. As this would be a decentralized solution grid load would be low. PV generated energy from home roof installations could be stored directly in the batteries and would not load the grid at all. Investment would be shifted to end users! Everything could be controlled via the real-time price. This seems to represent the beginning!

Much fewer e. g. hydro storage plants would be required then to support overall network regulation.

Weight probably is a problem as is space. They would be retrofitting existing buildings with little if any space outside. Think thin mini-splits lined up in street alleys such that a small car driving into their parking spot may only have a few inches on both sides.

Using lithium based chemistry also means they can leverage the battery designs for EV cars and consumer electronics.

Hi: Storage is great but why would anyone go Li when weight is not an issue?? My PV system has backup, 32 KWH for about $3500 in lead acid. SO $11K for less than 5 KWH to me is like buying gold plated batteries...
Poor choice for a non mobile storage medium...

.....Bill

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Junko Movellan is a Solar Industry expert who writes and analyzes the US and Japan PV downstream markets. She has more than 15 years of experience in the PV industry, analyzing industry trends and developing business strategies for global...